It doesn't "automatically" happen. How the process works depends on the school. If your school has previously sent kids to SAs, they probably have an established process. I will explain below what usually happens. But, at the end of the day, if you want a presentation to occur, it's up to YOU (NOT the school or the BGO) to make it happen.
You need to notify your career/college counselor that you have an appointment to a USNA (or to NAPS/Foundation) and that you'd like your BGO to make a presentation at the awards ceremony (or other event where such a presentation would be appropriate). The counselor (or the person in charge of the ceremony) should contact the BGO and work out logistics. Do NOT assume this has occurred. You may need to provide contact info for your BGO and/or may need to f/u with the BGO yourself. Please don't assume your BGO intuitively knows the date/time of your ceremony. We don't.
The BGO will try to attend -- it's one of the really fun things we get to do. However, it's not always possible. If you (or the career counselor) contacts the BGO well in advance, he/she will try to get a replacement to make the presentation. If all else fails, the BGO can provide a script for the presentation and someone from the school can do it. It's really nice if the presentation occurs early in the ceremony so that the BGO can leave immediately after, if desired, as the BGO may need to return to work and/or may not want to sit through several hours of ceremony for people he/she doesn't know.
I work with three schools. For two, it's a seamless, painless process. For the third, last year the ONLY reason I showed up was the parents and the appointee contacted me directly literally the day before the event. The career counselor had totally dropped the ball and failed to contact me regarding the ceremony despite being asked to do so (and telling the parents she'd done so). Luckily, timing worked out and I was able to show.
It's also nice to let the BGO know how much time he/she has for the presentation. At some schools, there are literally dozens of awards, so the "speech" needs to be VERY short (less than a minute). At other schools, a longer presentation may be appropriate. Finally, the candidate needs to bring the appointment certificate to the ceremony so the BGO can present it.
As noted, whether you have a presentation is entirely up to you. If you don't want one, then there need not be one. If you do want one, your BGO will be happy to oblige (schedule permitting).